U.S. patent application number 10/669276 was filed with the patent office on 2005-03-24 for system, kit, and method for measuring membrane diffusion.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Husberg, Michael L., McIntosh, Lester H. III, Rakow, Neal A., Roscoe, Stephen B..
Application Number | 20050063862 10/669276 |
Document ID | / |
Family ID | 34313693 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050063862 |
Kind Code |
A1 |
Roscoe, Stephen B. ; et
al. |
March 24, 2005 |
System, kit, and method for measuring membrane diffusion
Abstract
A system for measuring diffusion of a compound across a membrane
generally comprises a membrane held between a first base having a
plurality of outwardly extending hollow projections and a second
base fastened to the first base and having a plurality of recessed
tapered openings therein adapted to engage the plurality of hollow
projections. Methods for measuring membrane diffusion using such
systems are included. The system components are also provided in
kit form.
Inventors: |
Roscoe, Stephen B.; (St.
Paul, MN) ; Rakow, Neal A.; (Woodbury, MN) ;
Husberg, Michael L.; (West St. Paul, MN) ; McIntosh,
Lester H. III; (Green Lane, PA) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
34313693 |
Appl. No.: |
10/669276 |
Filed: |
September 24, 2003 |
Current U.S.
Class: |
422/68.1 ;
436/2 |
Current CPC
Class: |
G01N 2013/003 20130101;
B01L 3/5025 20130101; G01N 13/00 20130101; G01N 33/15 20130101;
G01N 2015/086 20130101 |
Class at
Publication: |
422/058 ;
436/002 |
International
Class: |
G01N 033/00 |
Claims
What is claimed is:
1. A system for measuring diffusion of a compound across a membrane
comprising: a first base having first and second opposed surfaces
and having a plurality of hollow projections extending outwardly
from the first surface, each hollow projection having a tapered tip
with an opening therein and a respective cavity contiguous with the
opening disposed within the projection; a second base having first
and second opposed surfaces, the first surface having a plurality
of recessed tapered openings therein adapted to engage the
plurality of hollow projections, each recessed tapered opening
being contiguous with a respective cavity that extends into the
second base; and a membrane contacting the recessed tapered
openings and the tips of the hollow projections, wherein the first
base is fastened to the second base by a first fastening means, and
wherein: a) each cavity within a hollow projection extends through
the first base and forms an opening at the second surface of the
first base; or b) each cavity within the second base extends
through the second base and forms an opening at the second surface
of the second base; or c) each cavity within a hollow projection
extends through the first base and forms an opening at the second
surface of the first base, and each cavity within the second base
extends through the second base and forms an opening at the second
surface of the second base.
2. The system of claim 1, wherein at least a portion of at least
the first or second base is transparent or translucent.
3. The system of claim 1, wherein the first fastening means is a
removable means.
4. The system of claim 1, wherein each cavity within a hollow
projection extends through the first base and forms an opening at
the second surface of the first base.
5. The system of claim 4, further comprising a first covering means
fastened to the second surface of the second base.
6. The system of claim 1, wherein the cavity in each hollow
projection extends into the first base.
7. The system of claim 1, wherein the cavity in each hollow
projection extends through the second base and forms an opening at
the second major surface of the second base.
8. The system of claim 1, further comprising a cover plate fastened
to the second surface of the first base.
9. The system of claim 8, wherein at least a portion of the cover
plate is transparent or translucent.
10. The system of claim 1, wherein the first and second surfaces of
at least one of the first and second bases are major surfaces.
11. The system of claim 1, wherein at least one of the first and
second bases comprises a plate.
12. The system of claim 1, wherein each tapered tip has a
cross-sectional profile that comprises at least one of an arcuate
portion or a beveled portion.
13. The system of claim 1, wherein each recessed tapered opening
has a cross-sectional profile that comprises at least one of an
arcuate portion or a beveled portion.
14. The system of claim 1, wherein the projections further comprise
a body portion having at least one wall.
15. The system of claim 14, wherein the body portion is
cylindrical.
16. The system of claim 1, wherein the membrane comprises a
synthetic polymer.
17. The system of claim 1, wherein the membrane comprises animal
tissue.
18. The system of claim 1, wherein the membrane comprises skin.
19. The system of claim 1, further comprising a retaining plate
having perforations therein adapted to allow the hollow projections
to pass therethrough, wherein the retaining plate is fastened to
the second base by a second fastening means, wherein the membrane
is disposed between the second base and the retaining plate.
20. The system of claim 19, wherein the second fastening means is
removable.
21. The system of claim 1, wherein each cavity within the second
base extends through the second base and forms an opening at the
second surface of the second base.
22. The system of claim 21, further comprising a covering means
fastened to the second surface of the second base.
23. The system of claim 21, wherein the cavity in each hollow
projection extends through the first base and forms an opening at
the second major surface of the first base.
24. The system of claim 23, further comprising a cover plate
fastened to the second surface of the first base.
25. The system of claim 24, wherein at least a portion of the cover
plate is transparent or translucent.
26. The system of claim 21, wherein the first and second surfaces
of at least one of the first and second bases are major
surfaces.
27. The system of claim 21, wherein at least one of the first and
second bases comprises a plate.
28. The system of claim 21, wherein each tapered tip has a
cross-sectional profile that comprises at least one of an arcuate
portion or a beveled portion.
29. The system of claim 21, wherein each recessed tapered opening
has a cross-sectional profile that comprises at least one of an
arcuate portion or a beveled portion.
30. The system of claim 21, wherein the projections further
comprise a body portion having at least one wall.
31. The system of claim 30, wherein the body portion is
cylindrical.
32. The system of claim 21, wherein the membrane comprises a
synthetic polymer.
33. The system of claim 21, wherein the membrane comprises animal
tissue.
34. The system of claim 21, wherein the membrane comprises
skin.
35. The system of claim 21, further comprising a retaining plate
having perforations therein adapted to allow the hollow projections
to pass therethrough fastened to the second base by a second
fastening means, wherein the membrane is disposed between the
second base and the retaining plate.
36. The system of claim 35, wherein the second fastening means is
removable.
37. A method of measuring diffusion of a compound through a
membrane comprising: providing a system according to claim 1;
placing a first fluid composition into at least one cavity in the
first base; placing a second fluid composition comprising a
compound into at least one cavity in the second base, wherein the
cavities in the first and second bases are in fluid communication
through the membrane; and analyzing the compound content of the
first fluid composition.
38. A method of measuring diffusion of a compound through a
membrane comprising: providing a system according to claim 4;
placing a first fluid composition into at least one cavity in the
first base; placing a second fluid composition comprising a
compound into at least one cavity in the second base, wherein the
cavities in the first and second bases are in fluid communication
through the membrane; and analyzing the compound content of the
first fluid composition.
39. A method of measuring diffusion of a compound through a
membrane comprising: providing a system according to claim 19;
placing a first fluid composition into at least one cavity in the
second base; placing a second fluid composition comprising a
compound into at least one cavity in the first base, wherein the
cavities in the first and second bases are in fluid communication
through the membrane; and analyzing the compound content of the
first fluid composition.
40. A method of measuring diffusion of a compound through a
membrane comprising: providing a system according to claim 21;
placing a first fluid composition into at least one cavity in the
second base; placing a second fluid composition comprising a
compound into at least one cavity in the first base, wherein the
cavities in the first and second bases are in fluid communication
through the membrane; and analyzing the compound content of the
first fluid composition.
41. A method of measuring diffusion of a compound through a
membrane comprising: providing a system according to claim 35;
placing a first fluid composition into at least one cavity in the
second base; placing a second fluid composition comprising a
compound into at least one cavity in the first base, wherein the
cavities in the first and second bases are in fluid communication
through the membrane; and analyzing the compound content of the
first fluid composition.
42. A system, in kit form, for holding a membrane comprising: a
first base having first and second opposed surfaces and having a
plurality of hollow projections extending outwardly from the first
surface, each hollow projection having a tapered tip with an
opening therein and a respective cavity contiguous with the opening
disposed within the projection; a second base having first and
second opposed surfaces, the first surface having a plurality of
recessed tapered openings therein adapted to engage the plurality
of hollow projections, each recessed tapered opening being
contiguous with a respective cavity that extends into the second
base; and means for fastening the first base to the second base
wherein: a) each cavity within a hollow projection extends through
the first base and forms an opening at the second surface of the
first base; or b) each cavity within the second base extends
through the second base and forms an opening at the second surface
of the second base; or c) each cavity within a hollow projection
extends through the first base and forms an opening at the second
surface of the first base, and each cavity within the second base
extends through the second base and forms an opening at the second
surface of the second base.
43. The system of claim 42, wherein each cavity within a hollow
projection extends through the first base and forms an opening at
the second surface of the first base.
44. The system of claim 43, further comprising: a retaining plate
having perforations therein adapted to allow the hollow projections
to pass therethrough; and means for fastening the retaining plate
to the second base.
45. The system of claim 42, wherein each cavity within the second
base extends through the second base and forms an opening at the
second surface of the second base.
46. The system of claim 45, further comprising: a retaining plate
having perforations therein adapted to allow the hollow projections
to pass therethrough; and means for fastening the retaining plate
to the second base.
Description
BACKGROUND
[0001] The development of transdermally deliverable pharmaceutical
compositions typically involves a screening and refinement process
in which a large number of pharmaceutical compositions are
evaluated. Typically the compositions include one or more
pharmaceuticals and one or more compounds (commonly known as
excipients or enhancers) that increase diffusion of the
pharmaceutical(s) across the membrane of interest (e.g., skin).
Hundreds of useful excipients are known, and the specific choice of
excipients for a given pharmaceutical typically involves an
extensive screening process involving many membrane diffusion
measurements.
[0002] Typical systems for measuring membrane diffusion have two
chambers separated by a membrane (e.g., skin). Typically, one
chamber contains a pharmaceutical composition to be tested (e.g.,
as a solution or in a transdermal patch), and the other chamber
contains a recipient solution representative of serum. The
pharmaceutical composition and the recipient solution each contact
opposite surfaces of the membrane. The concentration of the
pharmaceutical in the receiving solution is periodically measured
and the diffusion rate of the pharmaceutical across the membrane
determined. In order to obtain accurate membrane diffusion
measurements, it is typically important that air gaps between the
pharmaceutical composition, the receiving solution, and the
membrane be avoided.
[0003] Widely used commercially available systems of the
two-chamber type include Ussing chambers, Franz cells, in-line
cells, and horizontal cells. Many such devices are only capable of
making individual measurements and/or require relatively large
areas of membrane to operate.
[0004] Systems that can perform multiple diffusion measurements in
parallel using a single membrane have been reported. In essence,
such systems divide the membrane into a plurality of separate
regions, each of which serves as a membrane of a distinct
two-chamber type cell. In such systems, it is generally important
that the cells remain effectively isolated from each other (i.e.,
contents of one cell cannot enter into another cell).
[0005] There remains a need in the art for systems and methods that
are useful for rapidly screening large numbers of formulations
while efficiently using the membrane material.
SUMMARY
[0006] In one aspect, the present invention provides a system for
measuring diffusion of a compound across a membrane comprising:
[0007] a first base having first and second opposed surfaces and
having a plurality of hollow projections extending outwardly from
the first surface, each hollow projection having a tapered tip with
an opening therein and a respective cavity contiguous with the
opening disposed within the projection;
[0008] a second base having first and second opposed surfaces, the
first surface having a plurality of recessed tapered openings
therein adapted to engage the plurality of hollow projections, each
recessed tapered opening being contiguous with a respective cavity
that extends into the second base; and
[0009] a membrane contacting the recessed tapered openings and the
tips of the hollow projections, wherein the first base is fastened
to the second base by a first fastening means, and wherein: a) each
cavity within a hollow projection extends through the first base
and forms an opening at the second surface of the first base; or b)
each cavity within the second base extends through the second base
and forms an opening at the second surface of the second base; or
c) each cavity within a hollow projection extends through the first
base and forms an opening at the second surface of the first base,
and each cavity within the second base extends through the second
base and forms an opening at the second surface of the second
base.
[0010] In some embodiments, the system further comprises a
retaining plate having perforations therein adapted to allow the
hollow projections to pass therethrough, wherein the retaining
plate is fastened to the first base by a second fastening means,
wherein the membrane is disposed between the first base and the
retaining plate.
[0011] In another aspect, the present invention provides a method
of measuring diffusion of a compound through a membrane
comprising:
[0012] providing a system according to the present invention;
[0013] placing a first fluid composition into at least one cavity
in the first base;
[0014] placing a second fluid composition comprising a compound
into at least one cavity in the second base, wherein the cavities
in the first and second bases are in fluid communication through
the membrane; and
[0015] analyzing the compound content of the first fluid
composition.
[0016] In another aspect, the present invention provides a system,
in kit form, for holding a membrane comprising:
[0017] a first base having first and second opposed surfaces and
having a plurality of hollow projections extending outwardly from
the first surface, each hollow projection having a tapered tip with
an opening therein and a respective cavity contiguous with the
opening disposed within the projection;
[0018] a second base having first and second opposed surfaces, the
first surface having a plurality of recessed tapered openings
therein adapted to engage the plurality of hollow projections, each
recessed tapered opening being contiguous with a respective cavity
that extends into the second base; and
[0019] means for fastening the first base to the second base
wherein: a) each cavity within a hollow projection extends through
the first base and forms an opening at the second surface of the
first base; or b) each cavity within the second base extends
through the second base and forms an opening at the second surface
of the second base; or c) each cavity within a hollow projection
extends through the first base and forms an opening at the second
surface of the first base, and each cavity within the second base
extends through the second base and forms an opening at the second
surface of the second base.
[0020] In one embodiment, the kit further comprises a retaining
plate having perforations therein adapted to allow the hollow
projections to pass therethrough, and means for fastening the
retaining plate to the second base.
[0021] As used herein:
[0022] "membrane diffusion" refers to the rate of diffusion of a
compound through a membrane.
BRIEF DESCRIPTION OF THE DRAWING
[0023] FIG. 1 is a cross-sectional side view of an exemplary system
according to one embodiment of the present invention;
[0024] FIG. 2 is a cross-sectional side view of an exemplary system
according to one embodiment of the present invention;
[0025] FIG. 3 is a cross-sectional side view showing an exemplary
engaged tapered projection and tapered recess;
[0026] FIG. 4 is a cross-sectional side view showing an exemplary
engaged tapered projection and tapered recess;
[0027] FIG. 5 is an exploded perspective view of one exemplary
embodiment of the present invention; and
[0028] FIG. 6 is an exploded perspective view of one exemplary
embodiment of the present invention.
DETAILED DESCRIPTION
[0029] Referring to FIG. 1, exemplary system 100 for holding a
membrane comprises first base 150 having first and second opposed
surfaces 152 and 154, respectively. A plurality of hollow
projections 155 extend outwardly from first surface 152, each
hollow projection 155 having an outer wall 157 and tapered tip 160
with an opening 165 therein. Each hollow projection 155 has a
cavity 170 contiguous with opening 165 disposed therein.
[0030] Each cavity 170 has one or more sides 175. In one
embodiment, each cavity 170 has a respective bottom 180. Bottoms
180 may be at the same or different depths. In another embodiment,
sides 175 extend into first base 150, optionally extending through
the first base 150 to second surface 154 to form passages 185.
[0031] Second base 110 has first and second opposed surfaces 112
and 114, respectively. First surface 112 has a plurality of
recessed tapered openings 115 therein adapted to engage tapered
tips 160. Each recessed tapered opening 115 is contiguous with a
cavity 120 that extends into second base 110. Each cavity 120 has
one or more sides 125. In one embodiment, each cavity 120 has a
respective bottom 130. In another embodiment, the sides 125 extend
into second base 110, optionally extending through second base 110
to second surface 114 to form passages 135.
[0032] In typical use, membrane 190 is positioned between first
base 150 and second base 110, and first base 150 and second base
110 are fastened together by a fastening means, shown by screws 195
(which pass through holes 196 and engage threaded holes 197), such
that hollow projections 155 engage recessed tapered openings 115
with membrane 190 fixed therebetween.
[0033] In one embodiment, system 100 further comprises optional
retaining plate 106, which has perforations 108 therethrough
adapted to allow at least a portion of each hollow projection 155
(e.g., a portion of tip 160) to pass therethrough. For example,
perforations 108 may be of sufficient spacing and shape to permit
hollow projections 155 to simultaneously pass through perforations
108. Alternatively, the perforations 108 may be of sufficient
spacing and shape to permit, for example, only a portion of tapered
tips 160 to extend through perforations 108, but not allow hollow
projections 155 to simultaneously pass through perforations 108.
Retaining plate 106 is fastened to second base 110 by a second
fastening means shown by screws 119, which pass through holes 116
in retaining plate 106 and engage threaded holes 118 in second base
110.
[0034] In general, the optional retaining plate may be positioned
on either side of the membrane, and may be fastened to either the
first base or the second base. The retaining plate may assist in
maintaining membrane shape and integrity, and also allows the first
base to be unfastened from the second base-membrane-retaining plate
subassembly and refastened (e.g., to facilitate analysis of liquids
contains in cavities of the first base) without changes in membrane
position and/or the need to refill cavities in the second base with
liquid.
[0035] Referring now to FIG. 2, exemplary system 200 comprises
first base 250, having first and second opposed surfaces 252 and
254, respectively. A plurality of hollow projections 255 consisting
of tapered tips 260 extend outwardly from first surface 252, each
tapered tip 260 having an opening 265 therein. Each tapered tip 260
has a cavity 270 contiguous with opening 265 disposed therein.
[0036] Each cavity 270 has one or more sides 275. In one
embodiment, each cavity 270 has a respective bottom 280. In another
embodiment, the sides 275 extend into first base 250, and may even
extend through the first base to second surface 254, thereby
forming passages 285.
[0037] Second base 210 has first and second opposed surfaces 212
and 214, respectively. First surface 212 has a plurality of
recessed tapered openings 215 therein adapted to engage tapered
tips 260. Each recessed tapered opening 215 is contiguous with a
cavity 220 that extends into second base 210. Each cavity 220 has
one or more sides 225. In one embodiment, each cavity 220 has a
respective bottom 230. In another embodiment, sides 225 extend into
second base 210, and may even extend through second base 210 to
second surface 214, thereby forming passages 235.
[0038] In typical use, membrane 290 is positioned between first
base 250 and second base 210, and first base 250 and second base
210 are fastened together by a fastening means, shown by screws 295
(which pass through holes 296 and engage threaded holes 297).
[0039] The first and second bases and the retaining plate may be
made of any material, including, for example, metal, glass,
ceramic, plastic, and combinations thereof, and may be opaque,
transparent and/or translucent. The first and second bases may have
any shape (e.g., a block or plate) and/or thickness.
[0040] Systems according to the present invention may have any
number of hollow projections greater than one (e.g., 2, 12, 24, 32,
64, 96, or even as many as 256 hollow projections or more). Hollow
projections may individually have any shape including, for example,
cylindrical, prismatic, or conical shapes. Hollow projections may
have any, typically about equal, height relative to the base. Each
hollow projection has a tapered tip, which may be of any shape as
long as it generally narrows toward the outermost end of the
tapered tip.
[0041] Tapered tips may have any cross-sectional profile. Openings
in the tapered tips may have any shape, such as for example,
circular or polygonal. The area of the openings may be of any size,
for example, greater than about 0.01, 0.05, 0.1, 0.5, or even about
1 square centimeter, or even more.
[0042] Cavities in the hollow projections, and/or the first and
second bases may have any shape and/or depth, and their bottoms may
have any shape (e.g., flat and/or rounded).
[0043] Referring now to FIG. 3, the cross-sectional profile of one
or more tapered tips 324 may comprise an arcuate portion 340.
Referring now to FIG. 4, the cross-sectional profile of one or more
tapered tips 424 may comprise a beveled portion 440. In some
embodiments, the cross-sectional profile of the tip comprises a
beveled portion and an arcuate portion.
[0044] Similarly, recessed tapered openings may individually have
any shape, but are typically chosen to have a shape that is
complementary to tapered tips that they engage, in order that a
tight seal may be formed with a membrane when the tip and recessed
tapered opening are engaged with a membrane therebetween. Thus, as
shown in FIG. 3, the cross-sectional profile of recessed tapered
openings 315 may comprise an arcuate portion 345. Similarly, as
shown in FIG. 4, the cross-sectional profile of recessed tapered
openings 415 may comprise a beveled portion 445. In some
embodiments, the cross-sectional profile of the tip may comprise
both a beveled portion and an arcuate portion.
[0045] As shown in FIGS. 3 and 4, the tapered tips are adapted to
engage the recessed tapered openings fixing membrane 390 or 490,
respectively, therebetween.
[0046] Typically, the precise shape of the recessed tapered
openings and the tapered tips is not important, however to prevent
perforation of the membrane when assembling systems according to
the present invention, the depth of the recessed tapered openings
may be limited to less than about 1, 0.5, 0.3, 0.2, or even less
than about 0.1 centimeters, and the average angle of the taper may
be limited to less than about 45, 30, or even less than about 20
degrees from the surrounding surface.
[0047] Fastening means utilized in the present invention (e.g.,
means for fastening the first and second bases, means for fastening
the retaining plate to the second base, means for fastening the
covering means to the second base, and/or means for fastening the
cover plate to the first base) may be removable or non-removable.
Useful fastening means include mechanical, adhesive, and attractive
(e.g., magnetic, gravitational) means. Removable fastening means
include, for example, screws, removable adhesives, clamps, staples,
clips, nails, pins, hook and loop fasteners, weights, mushroom-type
mechanical fasteners, snaps and combinations thereof. Non-removable
fastening means include, for example, non-removable adhesives,
rivets, welds, locking snap connectors, soldered joints, and
combinations thereof.
[0048] During positioning the membrane between the first base and
the second base the membrane is typically smoothed (e.g., manually)
to remove wrinkles prior to fixing it in place (e.g., by fastening
a retaining plate to a base or by fastening the two bases
together).
[0049] Suitable membranes are typically thin soft pliable sheets
including, for example, synthetic polymer membranes (e.g.,
cellulose acetate sheets, polymeric membranes containing ethyl
cellulose, phospholipids, cholesterol, and mineral oil,
polyurethane polymers containing poly(ethylene glycol) block
segments, synthetic zeolites incorporated into poly(styrene),
silicone rubbers, laminated polymer sheets containing alternating
hydrophilic and hydrophobic sheets, filter papers or membranes
loaded with organic liquids, and cultured cell membranes); hairless
mouse skin; snake skin; pig skin; and cadaver skin. Further details
concerning suitable synthetic membranes that are useful as
substitutes for mammalian skin in permeation testing are described
by, for example, Houk et al. in "Membrane Models for Skin
Penetration Studies", Chemical Reviews (1988), vol. 88(3), pages
455-472, and by Hatanaka et al. in "Prediction of Skin Permeability
of Drugs. II. Development of Composite Membrane as a Skin
Alternative", International Journal of Pharmaceutics (1992), vol.
79, pages 21-28.
[0050] Systems according to the present invention may be used in
any orientation. However, to facilitate assembly it may be useful
to horizontally orient the bases while filling cavities therein and
assembling the system.
[0051] In typical use, one of the first or second bases is used as
a formulation plate that contains a plurality of compositions
comprising one or more compounds (e.g., pharmaceuticals,
excipients, dyes, chemical reagents and mixtures thereof,
nutriceuticals, vitamins, cosmoceuticals) to be evaluated and the
other as a receiving plate. For example, the second base may be the
formulation plate, and the first base may be the receiving plate,
or vice versa.
[0052] In one exemplary system 500, shown in FIG. 5, membrane 590
is positioned against formulation plate 510 thereby covering
recessed tapered openings 515 (not shown) in formulation plate 510.
Retaining plate 506, having perforations 508 therein, is fastened
to formulation plate 510 by means of screws 519, which pass through
holes 517 in retaining plate 506 and engage threaded holes 518 (not
shown) in formulation plate 510, thereby forming subassembly 502.
Subassembly 502 is fastened to receiving plate 550 by screws 595
that pass through holes 594 in formulation plate 510 and engage
threaded holes 596 in receiving plate 550. Advantageously, in this
embodiment subassembly 502 can be repeatedly fastened to, and
unfastened from, receiving plate 550 without having to handle
membrane 590.
[0053] Membrane 590 is typically smoothed (e.g., manually) to
remove wrinkles prior to fastening retaining plate 506 to
formulation plate 510. Compositions to be evaluated (not shown) are
placed into passages 535 in formulation plate 510, which are
covered by tape 537 to facilitate handling and/or to reduce
evaporation. Tape 537 may be replaced by other covering means such
as, for example, a cover plate.
[0054] Cavities 570 in hollow projections 555 of receiving plate
550 are filled with a receiving liquid (e.g., serum or a synthetic
version thereof, not shown). To help avoid the formation of air
gaps during assembly that may, for example, lead to erroneous
membrane diffusion rates, cavities 570 may be overfilled with
receiving liquid to the maximum point permitted by the surface
tension of the receiving liquid. Formulation plate 510 and
receiving plate 550 are then fastened together such that tapered
tips 560 engage recessed tapered openings 515, fixing membrane 590
therebetween. During this process, membrane 590 is typically
stretched across openings 570 in tapered tips 560 and compressed
between tapered tips 560 and recessed tapered openings 515, thereby
ensuring a tight seal and reducing, or more typically, eliminating
the possibility of crosstalk between adjacent cells. Elongated body
portions 556 of hollow projections 555 further help to prevent
crosstalk by allowing any liquids that leak out of one cell to
harmlessly drain away by gravity, for example, when the system is
oriented with hollow projections 555 extending vertically
upward.
[0055] Systems according to the present invention may further
comprise one or more covering means, for example, as shown in FIG.
5 by tape 537 and/or cover plate 578, that is present if cavities
570 extend through receiving plate 550. Suitable covering means
include, for example, films, sealing mats, plates, stoppers, and
combinations thereof. The covering means may be, for example, a
unitary covering means (e.g., a film, tape, or cover plate) or a
non-unitary covering means (e.g., a plurality of films, tapes,
stoppers, rubber septa, or a combination thereof).
[0056] In another exemplary system 600, shown in FIG. 6,
formulation plate 650 has hollow projections that consist of
tapered tips 660. Passages 685 (not shown) extend through
formulation plate 650 and form openings 665 in tapered tips 660.
Receiving plate 610 has recessed tapered openings 615 therein
adapted to engage tapered tips 660. Cavities 620 are contiguous
with recessed tapered openings 615. Receiving plate 610 is fastened
to formulation plate 650 by retaining bracket 672 and screws 662
that pass through holes 617 and engage threaded holes 618, such
that tapered tips 660 engage recessed tapered openings 615, fixing
membrane 690 therebetween. Receiving plate 610 is optically
transparent and retaining bracket 672 has perforations 629
therethrough of appropriate spacing and alignment to permit optical
detection of the contents of cavities 620.
[0057] Optical detection methods include, for example, visual
inspection, spectroscopic methods, optical scanners, and
videographic and photographic methods (including digital
photographic methods).
[0058] Systems according to the present invention may be used in
conjunction with various known collection, automated dispensing
equipment, and/or autosampling equipment. Examples of such
equipment include liquid handling robots, for example, such as
those commercially available from Gilson, Inc., Middleton, Wis. and
well plates (e.g., having 24, 96, or 384 wells) such as, for
example, those available from Weidmann Plastics Technology AG,
Rapperswil, Switzerland.
[0059] Systems according to the present invention may be provided
in assembled or kit form (i.e., unassembled or partially
assembled), with or without a membrane.
[0060] Various unforeseeable modifications and alterations of this
invention may be made by those skilled in the art without departing
from the scope and spirit of this invention, and it should be
understood that this invention is not to be unduly limited to the
illustrative embodiments set forth herein.
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